This invention relates to a fire retardant composition for use in treating cellulosic materials such as paper, wood and fiberboard. The fire retardant composition of this invention is highly effective, penetrates rapidly into the cellulosic material, is environmentally safe, and can be easily manufactured without the use of toxic materials or complex chemical reactions.
Residential and commercial fires annually claim the lives of hundreds of people and cause millions of dollars in property damage. As a result, increased attention has focused on methods for eliminating or reducing the risk of fire by increasing the use of detection methods and extinguishing systems, such as sprinkler systems, and by substituting fire retardant materials for combustible materials whenever possible. Although fire retardant materials, are somewhat more expensive than equivalent combustible materials, there use in high risk environments is becoming increasingly popular since this approach avoids many of the problems associated with active fire retardant systems, such as maintenance and operational difficulties. In effect, passive fire retardant systems have been found to be more cost effective than active systems in the long run since they do not require monitoring and are essentially foolproof
One problem associated with fire retardant materials is that they tend to have poorer physical properties and to be less aesthetically attractive than comparable materials which have not been treated for fire retardancy. Some fire retardant treatments tend to produce unsightly deposits on the surface of the treated cellulosic substrate, while others leave an undesirable film or residue. Still other fire retardant treatments involve the application of an intumescent paint to the substrate, which is an unsatisfactory approach for flexible substrates, and is also generally objectionable due to the charged appearance of the treated material. In addition, the fire retardant treatment may result in a loss of strength in the treated material which can be a serious disadvantage for some substrates such as fiberboard.
Another problem relates to the environmental safety of the fire retardant material and its components. Many of the organic materials which are used to manufacture fire retardants are complex brominated or chlorinated chemicals. These complex organics are not only unsafe to handle, but can also emit toxic fumes in the presence of a source of ignition. Toxic fumes are frequently more dangerous to humans than the fire which would result in the absence of the fire retardant treatment. Consequently, not only should the fire retardant reduce substantially the flammability of the substrate, but the substrate should also be safe to human occupants during flaming conditions.
Various fire retardant treatments for cellulosics have been proposed with varying degrees of success. U.S. Pat. Nos. 3,900,327 and 4,383,858 disclose flame retardants prepared by reacting, in different proportions, aqueous orthophosphoric acid and an alkylene oxide, preferably ethylene oxide or propylene oxide. This fire retardant is water-based, and is said to penetrate rapidly into the cellulosic substrate with only slight migration of phosphate salts to the surface of the substrate in highly humid atmospheres. However, alkylene oxides such as ethylene oxide and propylene oxide are highly toxic and potential carcinogens, and thus require extremely careful handling during the preparation of the fire retardant. Residues of the alkylene oxide may also remain in the finished fire retardant and the treated substrate, thus posing a further hazard to those who subsequently come in contact with these materials.